"No act of terror can match the strength and character of our country."

NEW YORK — President Obama led a somber yet spirited dedication of the National September 11 Memorial & Museum yesterday morning, where hundreds heard his message of resilience and hope in a cavernous hall at Ground Zero.

"No act of terror can match the strength and character of our country," Obama told the crowd of victims’ family members, survivors, rescue workers and officials at the start of the hourlong ceremony heralding the museum’s May 21 opening. "Nothing can ever break us. Nothing can ever change who we are as Americans."

Obama was introduced by former New York City Mayor Michael Bloomberg, the chairman of the memorial foundation, who acknowledged the emotional complexity of the $700 million museum.

The museum’s 10,000 artifacts and exhibits include victims’ personal effects, wrecked firetrucks, a video documenting the rise of al Qaeda and recordings of victims’ final phone messages.

"Walking through this museum can be difficult at times," Bloomberg said. "But it is impossible to leave without being inspired."

Attendees sat folding chairs set around a Ground Zero artifact known as the Last Column, a 36-foot, 58-ton pillar of welded steel that had helped support the inner core of the South Tower.

The column, which was the last one removed from the wreckage, is covered with tributes to emergency responders from colleagues, union workers and others who helped clear the ruined trade center site in what became known as The Pit.

Painted near the top of the column is "PAPD 37," "NYPD 23," and "FDNY 343," which indicate the number of Port Authority and New York City police officers and firefighters killed in the attack.

Obama and Bloomberg were joined by Gov. Chris Christie and former acting Gov. Donald DiFrancesco; New York Gov. Andrew Cuomo and former Gov. George Pataki; and New York City Mayor Bill de Blasio and Rudy Giuliani, who was mayor on Sept. 11, 2001.

Former President Bill Clinton and his wife, former Secretary of State Hillary Clinton, attended the ceremony but did not speak.

Aided by video projections on a concrete wall of the vast space known as Foundation Hall, the officials recounted acts of heroism depicted in the museum by police, firefighters and EMTs, and by ordinary citizens who displayed extraordinary courage and selflessness.

There was Welles Crowther, a 24-year-old stock trader from Rockland County known for the red bandana he always carried and used as a dust mask that morning, who carried a woman down 17 flights of stairs and kept going back up to lead others to safety — until the south tower collapsed.

In a short film, Todd Beamer’s father, David, talked about the Rolex watch, now in the museum’s collection, that would forever indicate the precise time his son and fellow passengers stormed the cockpit of United Flight 93. David Beamer described it as a "successful counterattack," that forced the plane down in a field in Shanksville, Pa, preventing the hijackers from reaching their Washington, D.C., target.

"In doing so, they changed the course of history," Cuomo said.

In a recording, the mother of Mark Bingham — who devised the cockpit plan with Beamer, Tom Burnett and Jeremy Glick — told how proud she was of her son.

Christie stood at a separate lectern and took over from Cuomo on cue, addressing the international outpouring of sympathy for Americans in response to the attack.

"While this happened on our soil, it happened to all of us," Christie, who was joined at the lectern by his wife, Mary Pat, said of the community of nations.

"Letters arrived from Australia and (the Republic of) Georgia; gifts from India, from Ireland and Kenya. People from all walks of life, CEOs down, helped us dig out from under and bandaged our wounds."

"The gift of friendship and fellowship can be born out of the night," Christie added, "for which we remain forever grateful."

In the original program, Christie’s speech was schedule to be followed by the Simon & Garfunkel song, "Bridge Over Troubled Water," performed by Broadway star Idina Menzel. Instead, there was an a capella performance of Amazing Grace, by Menzel’s "If/Then" Broadway co-star, Tony-winning actress and singer, LaChanze.

Music rang throughout the ceremony, which began with a youth choir singing "Somewhere," from "West Side Story." And in keeping with the program’s focus on the every day heroes of 9/11, it concluded with a brass ensemble’s rendition of Aaron Copeland’s "Fanfare for the Common Man."

Among the ceremony’s attendees was David Weild, a finance executive who lost several friends in the attack and founded Tuesday’s Children, a nonprofit group that works to ensure a bright future for the sons and daughters of 9/11 victims.

"Would somebody else have picked up the ball and done something for my kids?" Wield said, explaining his motivation during a brief interview before the ceremony.

One of the dedication’s last speakers was Donald DiFrancesco, whose brief tenure as New Jersey’s acting governor was marked by the trade center attack, which killed some 700 Garden State residents.

DiFrancesco praised the survivors, friends and family of victims, and compassionate strangers who, like Weild, responded to the attacks with acts of kindness or charity.

"What greater legacy can there be for the lives cut short," DiFrancesco suggested, "than the good works created in their name."